1. Field of the Invention:
This invention relates to spacers for a liquid crystal display device and more particularly to spacers for a liquid crystal display device which enable the opposed panels of the device to be held accurately at a fixed distance from each other.
2. Description of the Prior Art:
The liquid crystal display device is generally produced by interposing liquid crystal in a space formed with spacers between two vertically opposed transparent electrode substrates. The thickness of the layer of liquid crystal is controlled to a minute magnitude of the order of 10 microns. Since the electrooptical effect of the liquid crystal display device hinges heavily on the thickness of the liquid crystal layer, the function of the spacers for the liquid crystal display device which resides in controlling the thickness of the liquid crystal layer at the optimum value is important. Now that liquid crystal display are moving toward growth in size, the control of their liquid crystal layers in uniform thickness with high accuracy is becoming increasingly difficult and the possible dispersion of uniformity in thickness of their liquid crystal layer is increasingly liable to induce interference colors and uneven displays. Thus, materialization of means capable of keeping liquid crystal layers in liquid crystal display devices accurately in uniform thickness, namely enabling the vertically opposed two transparent electrode substrates in the devices to be kept separated accurately at a fixed distance from each other is a requisite indispensable to successful manufacture of liquid crystal display devices of high performance.
Heretofore, various materials have been tested for feasibility in spacers which serve to keep the vertically opposed two transparent electrode substrates of liquid crystal display devices at a fixed distance from each other. For example, spacers for liquid crystal display devices which are made of chopped glass fibers, metal oxides such as finely divided alumina particles, and thermoplastic resins such as spherical polystyrene particles have been developed. [Japanese Patent Laid-open Nos. SHO 57(1982)-70,522, SHO 57(1982)-210,323, SHO 56(1981)-40,809 and SHO 51(1976)-64,945.]
The conventional spacers, however, have been criticized as entailing various problems such as the difficulty encountered in keeping their liquid crystal layers uniform in thickness. In the case of spacers made of glass fibers, for example, there is the possibility that under the pressure exerted on the spacers when the vertically opposed two transparent electrode substrates are pressed against each other across the spacers during the manufacture of a liquid crystal display unit, the glass fibers of the spacers will be crushed and the spacers will consequently be deprived of their funtion. In the case of spacers made of metal oxide particles having high rigidity, the same pressure will possibly cause the particles to eat into the inner walls of the transparent electrode substrates and, in an extreme case, destroy the transparent electrodes formed on the substrates. In the case of spacers made of thermoplastic resin, when the thermoplastic resin is used as mixed in an adhesive sealing agent such as epoxy resin and polyimide resin or when it is subjected to a heat treatment for adhesion, there is the possibility that the spacers will be attacked by the adhesive agent or the heat and prevented from keeping the liquid crystal layer constant in thickness.
An object of the present invention is to provide novel spacers for a liquid crystal display device.
Another object of this invention is to provide spacers capable of keeping liquid crystal layer in a liquid crystal display device accurately in a uniform thickness.